GMW GMW17796 PDF

This standard describes the requirements for a coating system used to mitigate or eliminate galvanic corrosion between dissimilar metals and carbon fiber, especially threaded fastened joints.

Material Description. The barrier coating system is designed to mitigate or eliminate the galvanic reaction between dissimilar metals and carbon fiber. Note that this coating is not meant to protect the coated component against general corrosion. A separate base-finish may be necessary depending on application. Consult Materials and Fastening Engineering.

Symbols. Not applicable.

Applicability. This coating is suitable for internally and externally threaded parts (size greater than or equal to M6) and non-threaded ferrous parts where galvanic cell interactions exist and a high level of corrosion protection is required. This is not recommended for the following without Materials/Fastening Engineering approval:

Bolts and nuts of sizes < M6.

Loose washers of all sizes.

Parts where electrical conductivity is required.

Remarks.

The material covered in this specification may not be suitable for all components. Each application must be reviewed with the responsible Materials Engineer before usage.

Use of this coating system on threaded surface and/or bearing surface of joints may affect the torquetension relationship. The coating system shall have an integrated or separately applied lubricant to address general assembly requirements as defined in 3.9.1. However, a torque-tension study of the fastener joint before releasing this coating on new applications is recommended.

The material in this specification is suitable for temperatures up to 150 °C. Consult Materials Engineering for higher temperature applications.

The coating is generally thicker than common fastener coatings, and may not be compatible with smaller internal drive fasteners. This may be accommodated by oversizing the fastener internal drive. Consult Fastening Engineering for these types of fasteners.